I. Field of the Invention
The present invention relates to data communications. More particularly, the present invention relates to method and apparatus for efficiently processing a received signal in a communications system.
II. Description of the Related Art
In a typical digital communications system, data is processed at a transmitter unit, modulated, conditioned, and transmitted to a receiver unit. The data processing may include, for example, formatting the data into a particular frame format, encoding the formatted data to provide error detection/correction at the receiver unit, channelization (i.e., covering) of the encoded data, spreading the channelized data over the system bandwidth, and so on. The data processing is typically specifically defined by the system or standard being implemented.
At the receiver unit, the transmitted signal is received, conditioned, demodulated, and digitally processed to recover the transmitted data. The processing at the receiver unit is complementary to that performed at the transmitter unit and may include, for example, despreading the received samples, decovering the despread samples to generate decovered symbols, decoding the decovered symbols, and so on. Due to multipath and other phenomena, the transmitted signal may reach the receiver unit via multiple signal paths. For improved performance, the receiver unit is typically designed with the capability to process multiple (and strongest) instances of the received signal.
To perform the required signal processing, some conventional receiver units are designed with a number of processing elements, with each processing element being designed especially for, and dedicated to perform, a specific function. For example, a receiver unit may be designed with a searcher element and a number of data processing elements. The searcher element searches the received signal for strong signal instances, and the data processing elements are assigned to process specific signal instances of sufficient signal strength. Implementation of multiple parallel processing elements results in increased circuit complexity and costs. The processing elements are also typically of fixed designs, and no programmability is typically provided (e.g., to process the received signal with different sets of parameter values to perform, for example, pilot processing, signal searches, and data demodulation). Moreover, the number of signal instances that can be processed is limited to the number of processing elements implemented.
To reduce complexity, some other conventional receiver units are designed with a number of parallel front-end units coupled to a common datapath processor. Each front-end unit performs partial processing (e.g., despreading and decovering) of an assigned signal instance. The common datapath processor then performs the remaining processing (e.g., demodulation with the pilot, energy calculation, and so on) on the partially processed data. Again, a limited number of signal instances can be processed based on the number of front-end units implemented, and no programmability is typically provided.
For a user terminal, the ability to process many instances of a received signal can provide improved performance. For a base station, multiple signal instances for multiple users are typically required to be processed concurrently, thus further highlighting the need for efficient signal processing techniques. The ability to process signals for multiple users using a small number of signal processing elements is economically and technically desirable for various reasons such as, for example, higher board density, fewer component count, lower costs, and so on. Programmability in the signal processing elements is also desirable in communications systems that can transmit data using various parameter values (e.g., different channelization codes of various lengths) depending on various factors such as, for example, the data rate of the transmission.
As can be seen, techniques that can allow for efficient processing of a received signal in a communications system are highly desirable.